Fuel tanks on board vehicles of various kinds generally have to meet sealing and permeability standards in relation to the type of use for which they are designed and the environmental requirements that they have to satisfy. At the present time, both in Europe and throughout the world, there is a substantial tightening of the requirements regarding the limitation of pollutant emissions into the atmosphere and into the environment in general.
To limit these emissions, care is taken in particular to position the components (ventilation lines, valves, baffles, stiffeners, etc.) inside the tank and/or the fill pipe (see in particular application WO 2004/024487 in the name of the Applicant). However, when these elements are fastened to the tank after it has been molded, it is generally necessary to make at least one opening in the tank so as to be able to introduce these elements into the tank and to fasten them thereto. Hence there may be potential sealing and permeability problems near this opening. The leaktight closure between an element and the tank is conventionally achieved with the aid of the compression of a seal, which seal is however a significant source of permeability. Furthermore, this type of closure is generally performed manually on the production line, which creates labour costs and may generate scrap due to human error.
Several years ago the Applicant therefore developed a process of initially molding a cut parison (cut into 2 sections) in order to be able to introduce thereinto and fasten thereto components during the actual molding of the tank and to thus avoid piercing openings (see patent EP 1 110 697 in the name of the Applicant).
This process has since been the subject of several improvements targeting particular means for fastening these components: see in particular applications WO 2006/008308 (fastening of components by rivet punching), WO 2006/095024 (fastening of ventilation lines that have a part that can be deformed due to the presence of a bend that is stretched during the attachment of these lines to the parison) and WO 2007/000454 (fastening of components according to an ideal layout and in particular, as regards the ventilation lines, while avoiding the formation of siphons).
These improvements have been able to be made due to the use of a core, i.e., a part of suitable size and shape for being able to be inserted between the impressions of the mold when the parison is located therein and to fasten thereto the components inside the tank without the edges of the parison being welded (since the core must be removed before the final molding of the tank, a step during which the welding of the parison sections is carried out). Such a part (core) is, for example, described in patent GB 1 410 215, the content of which is for this purpose incorporated by reference into the present application.
In particular, the aforementioned application WO '454 describes a process that uses such a core in order to position on the parison at least one portion of a component intended to pass through the wall of the tank. The variants illustrated in this application require either a manual assembly step after all (with the aforementioned risks of error and handling costs), or the deformation of the parison by piercing in order to allow a portion of the component to pass through, hence a risk of damaging said parison.
U.S. Pat. No. 6,860,398, which relates to conventional processes (twin-sheet thermoforming or blow-molding of a single parison) for manufacturing a tank, also describes a method for fastening a component (fitting) during this process and which consists in sandwiching the sheet/parison between the outer and inner parts of said fitting, which is in fact made of two parts. Such a process is also capable of damaging said sheet/parison (indeed, the EVOH layer risks being very greatly reduced in thickness and, in an extreme case, breaking and thus no longer ensuring the impermeabilization of the filler neck) and also involves the fastening of two parts, which is complicated and costly.
Moreover, the neck that is described in this application is intended to connect a sleeve thereto using a clamp collar. At the other end of this sleeve the fill pipe is then connected. The material used for this sleeve is typically of low permeability. Thus, the permeability of the assembly between the filler neck and the sleeve is characterized by the distance between the EVOH layer in the filler neck and the sleeve. It is then therefore advantageous to position the EVOH layer as close as possible to the sleeve. However, in the variant that is the subject of this application, this distance is increased by the part 22 of FIG. 6.